Copenhagen summit urges immediate action on climate change

Climate experts who met this week in Denmark have warned that the overall prognosis on climate change is worse than previous estimates have suggested.

More than 2,000 delegates - including climatologists, social scientists and economists - from 80 nations gathered for the International Scientific Conference on Climate Change in Copenhagen from 10–12 March. Their goal was to provide a scientific update to the Intergovernmental Panel on Climate Changes (IPCC) 2007 assessment on global warming.

The latest results made for bleak listening at times. Scientists cautioned that some of the impacts of global warming, such as sea level rise and loss of summer sea ice in the Arctic, are happening much sooner and more severely than scientists had estimated just two years ago. "What we are seeing now is that some aspects are worse than expected," says Stefan Rahmstorf, head of Earth System Analysis at the Potsdam Institute for Climate Impact Research in Germany and a plenary speaker at the congress.

Addressing congress delegates this morning, economist Nicholas Stern said that policymakers now need to consider the consequences of temperature rises of 6??C or more. Stern, who conducted a review in 2006 of the economic effects of climate change on behalf of the British government, was not alone in expressing a growing sense of urgency to policymakers.

On 10 March, climatologist Konrad Steffen of the University of Colorado at Boulder said that sea levels could rise as much as 1 metre by 2100, according to new analyses of ice loss from Greenland. The top estimate from the IPCCs 2007 report was a rise of 0.59 metres by the end of the century.

The information presented this week in Copenhagen will form the basis of a 30-page document, to be published in early June. Though the document will be peer reviewed, it will not have the rigor or the authority of the IPCC assessments. The IPCCs fourth assessment report in 2007 evaluated peer-reviewed research that was published before 2006, a process that involved more than 2,500 experts and over 130 nations. "The IPCC process is slow and it tries to go for a consensus view. The output from this conference will hopefully be a majority view but its unlikely to be a consensus view," says Jason Lowe, Head of Mitigation Advice at the UK Met Office. "The real value in the updated assessment is how current it will be."

In December this year, parties to the United Nations Framework Convention on Climate Change (UNFCCC) will descend on Copenhagen to wrangle over the details of a new global climate deal ?? a potential successor to the Kyoto Protocol. Although the outcome of this weeks conference will not officially inform the UNFCCC meeting in December, it will help "decision makers understand the extent of change and the urgent need to make a decision about how to respond", says Katharine Richardson, congress chair and biological oceanographer at the University of Copenhagen.

Failing to permeate

But at the conference, there was a growing fear that the message is simply failing to permeate. "Im frustrated, as are many of my colleagues, that 30 years after the US National Academies of Science issued a strong warning on CO2 warming, the full urgency of this problem hasn dawned on politicians and the general public," says Rahmstorf.

Thats not necessarily the fault of policymakers, says Martin Parry, former cochair of the IPCCs working group on climate impacts and adaptation, and also at the UK Met Office. "Its a pity that the IPCC was unable, two years ago, to assess the array of options for avoiding dangerous climate change," says Parry. The UN climate body has not yet analyzed how specific policy actions, such as targets for decreasing emissions, would impact the rate of climate change. "Now we have a situation where the scientific knowledge on mitigation is still evolving, which doesn leave time for due consideration by policy makers," he adds.

Delegates agreed that more stringent and urgent action is needed in order to avoid dangerous climate change, currently defined by the European Union as a temperature rise of more than 2??C above preindustrial values. But whether that goes far enough, and whether its even achievable, is another issue. "If we look at all of the impacts, well probably decide that two degrees is a compromise number, but its probably the best we can hope for," says Rahmstorf.

In a paper published this week in Environmental Research Letters1, Lowe and colleagues concluded that if emissions peak by 2015 and are decreased 3% per year thereafter, there is a 55% chance of exceeding a 2??C rise in global average temperatures, and a 1 in 3 chance that the world will still be more than 2??C warmer in 100 years time.

Getting emissions to peak in 2015 is "going to be tough" says Parry. But it could be achieved by aiming for an 80% decrease in CO2 emissions by 2050, starting now. "We need hard targets to be agreed in December that state when we start and how much we do," he says. "A clear statement from 2,000 scientists should certainly make a difference."